1,3-Butadiene is a highly important key substance in the chemical industry that has been used as a raw material for various chemical products. Chemical products including synthetic rubbers such as styrene-butadiene rubbers, polybutadiene rubbers, and chloroprene rubbers, as well as ABS resins, adiponitrile and 1,4-butanediol have been produced by using 1,3-butadiene as a raw material. As industrial methods for producing 1,3-butadiene, a production method by separating 1,3-butadiene from B-B fraction (a mixture containing C4 olefins mainly) generated by carrying out naphtha cracking, a production method by dehydrogenating butane or butene, or the like has been known (Non Patent Document 1).
3-Buten-2-ol is a useful substance that can be converted to 1,3-butadiene by dehydration. Examples of a method for converting 3-buten-2-ol to 1,3-butadiene include a method for dehydrating 3-buten-2-ol in the presence of silica-alumina catalyst as disclosed in Non Patent Document 2. 3-Buten-2-ol is a useful substance that can be converted to 1,3-butadiene and can be used as a raw material of pharmaceuticals or the like (Non Patent Document 3, Non Patent Document 4). As methods for producing 3-buten-2-ol, Non Patent Document 5 discloses a production method by reacting methylmagnesium iodide with acrolein, and a production method by partially oxidizing 2-butanol; and Patent Document 1 discloses a production method by reducing methyl vinyl ketone.
On the other hand, in recent years, the problem of global warming caused by greenhouse gases such as carbon dioxide generated from fossil resources, or the problem of depletion of fossil resources is growing into a serious problem. Owing to this, necessities for preventing the global warming and shifting to sustainable recycling-oriented society are increasing. In chemical industries, it is an urgent task to construct techniques to produce various chemical products from substances derived from biomass resources which are renewable resources. Both the above-mentioned 1,3-butadiene and 3-buten-2-ol are produced by using fossil resources as raw materials, and it is therefore very important to shift the raw materials to biomass resources in view of global environmental protection and reduction of fossil resources.
Since 2,3-butanediol can be produced by microbial fermentation using sugars as a raw material, it is a substance derivable from biomass resources (Non-patent Document 6). Thus, if 2,3-butanediol can be converted to 1,3-butadiene and/or 3-buten-2-ol, the raw materials of 1,3-butadiene and/or 3-buten-2-ol can be then shifted to the biomass resources.
The reaction to convert 2,3-butanediol to 1,3-butadiene is a dehydration reaction to eliminate two water molecules from 2,3-butanediol, and the reaction to convert 2,3-butanediol to 3-buten-2-ol is a dehydration reaction to eliminate one water molecule from 2,3-butanediol. Although the dehydration reaction of 2,3-butanediol is known to proceed by using an acid catalyst, the main product is methyl ethyl ketone in many cases.
As methods for converting 2,3-butanediol to 1,3-butadiene, a conversion method by dehydration reaction using thorium oxide as a catalyst (Non-patent Document 7), a conversion method by dehydration reaction using cesium oxide-silica complex as a catalyst (Patent Document 2), a method for reacting 2,3-butanediol with acetic acid to obtain 2,3-diacetoxybutane, and then thermally decomposing and converting the obtained 2,3-diacetoxybutane to 1,3-butadiene (Non-patent Document 8), and the like are known.
As methods for converting 2,3-butanediol to 3-buten-2-ol, a conversion method by dehydration reaction using thorium oxide as a catalyst (Non-patent Document 7), and a conversion method by dehydration reaction using a catalyst containing hydroxyapatite (Non-patent Document 3) are known.
The reaction to dehydrate 2,3-butanediol to produce 3-buten-2-ol belongs to a reaction to dehydrate a secondary alcohol to produce 1-alkene. As an example of reactions to produce 1-alkene in preference to 2-alkene from a secondary alcohol, Non-patent Document 9 discloses a method to dehydrate 4-methyl-2-pentanol to produce 4-methyl-1-pentene selectively. As catalysts for promoting this reaction, scandium oxide, cerium oxide, ytterbium oxide, samarium oxide and the like are disclosed.